In the past, a luminaire is proposed that controls a conduction phase of a lighting load such as a light-emitting diode (LED) and dimly lights the lighting load. “Dim” means adjusting the brightness of lighting. A dimming operation terminal device in such a luminaire is connected between an alternating-current power supply and the lighting load and subjects a load current to phase control. Such a dimming operation terminal device of a phase control system is provided to be embedded in or exposed from a wall or the like. An operator can operate a rotary or sliding operation tool provided on the front surface of the dimming operation terminal device, change a conduction phase of a phase control type dimmer, and change the brightness of a lighted place lighted by the lighting load to desired brightness.
Such a phase control type dimmer subjects a power supply voltage itself supplied to the lighting load to phase control. Usually, such a phase control type dimmer is referred to as two-wire dimmer.
On the other hand, a dimmer of a type for transmitting, via a signal line separated from a power supply line, a dimming signal to a lighting device that lights a lighting load is proposed. Such a dimmer of the type for transmitting the dimming signal via the signal line is sometimes referred to as four-wire dimmer.
In the past, a dimmer is known that lights an LED (light-emitting diode) using a boost chopper circuit, transmits a duty-variable (PWM-controlled) dimming signal from a dimming operation terminal device via a signal line, and controls an output of the boost chopper circuit to dimly light the LED.
In general, such a dimming operation terminal device that generates the duty-variable dimming signal obtains a voltage for dimming operation from an alternating-current power supply. In such a case, in general, a commercial alternating-current voltage is stepped down by resistance division, a transformer, or the like and then rectified and smoothed (further converted into a constant voltage according to necessity) to obtain a desired direct-current voltage.
However, a power supply for the dimming operation terminal device in the past explained above needs to step down a relatively high-voltage alternating-current power supply to generate a relatively low voltage. Therefore, the power supply has a complicated configuration and the terminal device tends to be increased in size. If the dimming operation terminal device is not sufficiently electrically insulated from the alternating-current power supply and a lighting device, safety against an electric shock of the operator is not guaranteed. When plural dimming operation terminal devices are provided in parallel, electrical insulation needs to be sufficiently taken into account. When another electric appliance such as an intercom and the dimming operation terminal device are set adjacent to each other at home, electrical insulation between the terminal device and the other appliance needs to be sufficiently taken into account. In order to secure such insulation, the dimming operation terminal device is often requested to have a complicated configuration.
When a power supply for the dimming operation terminal device is formed using an insulated step-down transformer, the power supply has a complicated configuration and is increased in size. Besides the dimming operation terminal device that includes the power supply for dimming operation by itself and transmits a duty-variable (PWM-controlled) dimming signal, there is a dimming operation terminal device that does not include a power supply for operation by itself and causes a lighting device to generate a dimming signal according to operation. In such a dimming operation terminal device, for example, a variable resistance section is provided in the dimming operation terminal device, a voltage is supplied from a lighting device side to the variable resistance section, and the dimming operation terminal device changes the resistance of the variable resistance section to thereby transmit a variable voltage signal to the lighting device side. In this case, the dimming operation terminal device is also requested to be electrically insulated from the alternating-current power supply and the lighting device side.
Therefore, there is a demand for a luminaire in which a dimming operation terminal device is electrically insulated from an alternating-current power supply and a lighting device, a power supply section of the dimming operation terminal device has a relatively simple configuration and is reduced in size and in weight.